The present invention relates to a water gate and, more particularly, a water gate adapted to automatically respond to the buildup of water pressure.
The use of water or flood gates is well known. Typically, such gates are built in at the top of a dam such that they may be opened to allow water above a certain level to escape and relieve pressure on the dam. Additionally, such water control gates may be used to allow logs, ice, or other floating debris to pass by a dam without damaging it.
Generally, such water control gates have either been operator controlled or automatically responsive. The operator controlled gates are those which move from a water holding position to a water releasing position in response to the control of a human operator, whereas the automatically responsive water control gates move from a water holding position to a water releasing position automatically in response to a predetermined water level and/or water pressure.
The operator controlled water gates are disadvantageous in that the requirement for a human operator adds greatly to the cost of operating the system. In addition, it is very difficult for a human operator to keep track of conditions along the length of a large dam. Of course, if the operator is to cause a water control gate to be opened so as to prevent a log or other floating debris from damaging the dam, he must be aware of floating debris at any point along the length of the dam.
To avoid the problems associated with operator controlled water gating systems, the prior art includes numerous automatically responsive water control gates. The following U.S. patents disclose such automatically responsive water control gating systems:
No. 625,506--Hone May 23, 1899 PA0 No. 1,184,062--Bebout May 23, 1916 PA0 No. 1,389,212--Parker Aug. 30, 1921 PA0 No. 1,938,675--Young Dec. 12, 1933 PA0 No. 4,073,137--Nomura Feb. 14, 1978
The Hone patent uses a lower sliding gate which is connected to an upper pivoting gate by way of a cable and pulley arrangement. When sufficient pressure is exerted on the upper gate, it will pivot to a water releasing position and in turn use the cable to lift the lower gate, thereby allowing water to escape adjacent the lower gate in addition to water escaping adjacent the upper gate.
The Bebout patent discloses a movable dam section which may be automatically operated when the water reaches a certain level. Specifically, when water enters bucket 27 (FIGS. 4 and 5) this causes the latch 19 to be moved, which in turn allows the movable dam section 1 to assume a water releasing position.
The Parker patent discloses a water control gating system useful for tide waters. In particular, Parker uses a coiled torsion spring (see especially FIG. 4) to allow tide water to return to the ocean.
The Young patent discloses a water control gate which pivots about axis 31 (FIG. 1) in response to water pressure overcoming weight 35 which tends to hold the gate 13 in a water retaining position. When the pressure exerted by the water diminishes sufficiently, the force exerted on gate 13 by weight 35 will cause the gate 13 to reassume an upright water holding position. The system disclosed in this patent includes a series of adjacent water controlling gates with a sealing strip 21 (FIG. 4) to prevent water leakage between adjacent gates.
The Nomura patent shows a hydraulic water gating control system including a helical spring which moves a gate between a water holding position and a water releasing position depending on the pressure on the gate.
Prior art automatically controlled water gating systems are subject to one or more of several disadvantages. Specifically, they have been prone to jamming as where a hinge, cable, or other movable part is subject to the water on the upstream (dam) side of the gate. Those gates which are designed to pass water over and under the gate are especially difficult in this regard in that a semi-submerged debris may jam on the under side of the gate. Also prior art water control gates are often subject to failure due to water induced corrosion of movable parts exposed to water on the upstream side of the gate.
Prior art water control gates using helical springs to bias the gate closed (in a water holding position) are disadvantageous in that material may be wedged in between the coils of the helical spring thereby disabling it. As a protective measure, the helical spring or springs may be shielded from possible jamming by debris, but this requires complex and difficult to manufacture structures.